Ball and socket joint



Sept. 3, 1963 F. G. REUTER ETAL 3,102,744

BALL AND SOCKET JOINT Filed March 23, `1960 United States Patent fl i ce3,102,744 Patented Sept. 3, 1963 3,102,744 BALL AND SOCKET JOINT FranzG. Reuter and Jrgen Ulderup, Lemforde, Germally, RSSlgD'ors, by mesneassignments, to Mobay Chemical Company, Pittsburgh, Pa., a corporationof Delaware Filed Mar. 23,1960, Ser. No. 17,069 Claims priority,application Germany Mar. 26, 1959 6 Claims. (Cl. 287-87) .This inventionrelates generally to ball and socket jomts adapted for use in thesteering mechanism of a vehicle aud more particularly fto an improvedball and socket joint having a resinous liner between the ball andsocket.

It has been proposed heretofore to provide ball and socket joints with aseparate resinous liner y(i.e. uonadherent liner) between the ball andsocket. The purpose of these separate liners is rto provide an elasticbearing surface for the ball of the king pin which absorbs shock'transmitted from the wheels to the joint as the wheels pass over a roadsurface. Joints of this type are so iiexible, however, that theyintroduce play into the steering mechanism. Consequently, the driverscontrol over the steering, or feel, is impaired and the road stabilityof the vehicle is jeopardized because a Wheel lheld by the tie` rod in-an elastic joint does not track as faultlessly as one which ispositioned by a joint entirely free of play.

lt is therefore an object of the invention to provide Ian improved balland socket joint. Another object of the invention is to provide a balland socket joint having a resinous separator which is devoid of thedisadvantages inherent in the prior joints of this type.

Other objects will become apparent from the following description withreference to the accompanying drawing in which:

FIGURE 1 is a longitudinal fragmentary section of one embodiment of theinvention;

FIGURE 2 is a longitudinal `fragmentary section of another embodiment ofthe invention; and

FIGURE 3 is a section through an embodiment of a bearing cup for use ina joint provided as an embodiment of this invention.

The foregoing objects `and `others are accomplished in accordance withthis invention, generally speaking, by providing a ball and socket jointhaving a king pin terminating in a spherical head positioned in abearing housing having an adherent coating of an abrasion resistantsynthetic resin which lies between the housing and spherical head. Ithas been found that it is not necesasry for a ball joint to have elasticbea-ring surfaces. A relative thin adherent coating of a synthetic resinhas been found to dampen vibrations. The invention thus provides theball joint housing Wit-h an adherent, thin, synthetic resinous coatingwhich acts as a low friction bearing surface. FPhe thin, syntheticresinous coating dampens the vibrations ordinarily transmitted in asteering mechanism without producing any play therein. The thickness offthe coating can be varied depending upon the weight of the vehicle andthe type thereof. L'For example, the coating on a ball joint used intrucks will be thicker than one used in a ball joint used for thesteering mechanism of a passenger vehicle. As a general rule, however,it is preferred that the thickness of the coating be from about 0.001inch to about 0.05 inch but any thickness which will effect dampeningwithout introducing play in the steering mechanism may be used.

In one embodiment of the invention, the housing is provided with a rigidbearing cup which lies against the upper surface of the spherical head.-In this embodiment, the coating is applied to the housing adjacent thei of the synthetic resin over the surface thereof and permitting thesolvent in the solution to evaporate. 'I'he synthetic resin may be apolyester, a polycarbonate, a polyamide, apolytetralluoromethane orsimilar abrasion resistant resin; However, best results are obtainedwit-h a poly-urethane elastomer so it is preferred to use this resinyfor lining the housing and the bearing cup. The solution may containthe resin dissolved in any suitable inert solvent therefor such as, forexample, ethyl atate, acetone, mineral spirits, dimethyl fOrmamide, orthe like. The polyurethane coating can be applied by reacting thechemicals in a solvent therefor after the coating has been applied. Anysuitable polyester such as one prepared by esterifying a polycarboxylicacid and a polyhydric alcohol may be used; Such polyesters or alkydresins are known in the art. The polycarbonate may be prepared inaccordance with the process disclosed in Canadian Patent 578,585,granted .lune 30, 1959. Polyamides are known in the trade yas Nylon andany such resin may be used. The polyurethane elastomer may be preparedin accordance with the process disclosed in Reissue Patent 24,5114(2,729,618) or by any `other suitable process from a polyalkylene etherglycol or a polyester. Preferably, the polyurethane elast-omer shouldhave a Shore A hardness -of .from about to about 98. Any of thesesynthetic materials have sufficient ldampening properties, strength andabrasion resistance to perform satisfactorily as a coating in a ball andsocket joint. The synthetic resin can be further improved byincorporating particles of molybdenum disulfide therein. rfhe molybdenumdisulfide should preferably have a cross-sectional dimension .of fromabout 0.002 millimeter to about 0.02 millimeter. It is advantageous toinclude a silicone oil or a suitable liquid hydrocarbon along with themolybdenum disulfide. Any suitable liquid organo siloxane may be used asthe silicone oil. Preferably, the silicone oil should have a viscosityof from about 50 to 500 centistokes at 20 C. Preferably, from about.0.01 percent to about 5 percent by weight, based on the Weight of theresin, orf the molybdenum disulfide should be used. Preferably, fromabout 0.01 percent to about 5 percent by weight silicone oil `orhydrocarbon should be used.

'flhe rigid bearing oup used in some embodiments of the invention can beone of conventional design. However, it is not necessary to machine thebearing cup to as close tolerances when using the coating as it has beenheretofore. Because a greater tolerance is permissible, it is possibleto use bearing cups made by sintering, pressing or casting Without anysubsequent machine operations. In rfact, it is advantageous not tomachine the surface which is to have the synthetic resinous coatingbecause adhesion of the coating is lbetter on ,fthe unmachined surfacethat it is `on a machined surface.

In another embodiment of the invention, which is a preferred embodimentbecause it is more ecient in dampening noises and vibrations, a wovencore of a suitable textile is placed on the surface of the housing orbearing cup and the synthetic resinous coating; is applied over thecore. core may be of 'any suitable textile such as a polyamide ber,cotton or the like. The core improves the strength of the coating andprevents disadvantageous elasticity of the coating.

`Referring now to the drawing Vfor a more detail description of theinvention, FIG. l illustrates one embodiment in which king pin 1terminates in a spherical head 2 which is positioned inside a bearinghousing '3'. A coating cup has a surface of the type obtained when it isv formed without machining such as by pressing, casting, or a sinteringoperation. Coating 4a of polyurethane elastomer' adheres to the innersurface of bearing cup 5. A compression spring 6 holds beaming cup 5 inposition in the conventional manner. Both lcompression spring 6 bearingcup 5 are located 4and secured inside a lid 7 Which is threadablymounted on housing 3.

'The embodiment shown in FIG. 2 is a ball joint generally similar to theone illustrated in FIG. l. King pin 1 has its spherical head 2positioned inside a housing 3. A beaming cup 5 having a coating ofpolyurethane elastomer 4a lies in the upper part of the housing. Thelower par-t of housing 3 has a bearing cup 8 which is coated with apolyurethane elastomer 4a. Beaning cup 8 and bearing cup 5 are similarin design and either or both can be made by sintering or other process.

A bearing cup is illustrated in lFIG. 3 which is provided with la thickcoating of a syntheticresin. A coating of this type may be required whena resin such as tetrauoroethylene lis used. Coating 4b on bearing cup 5has embedded therein a Woven cloth core 9. Reinforcing textile core 9increases the strength and rigidity of the coating.

Although the invention has been described in considerable detail lin theforegoing dor the purpose of illustration, it is to be understood thatsuch detail is solely for this purpose and that variations can be madetherein by those skilled in fthe art Without departing from the spiritand scope of the invention except las is set forth in the claims.

What is 'claimed is:

l. A ball and `socket joint having a housing having a socket and a ballpositioned in the socket, a thin selfadhering coating comprising asubstantially non-porous polyurethane elastomer having particles of asolid lubriil vcant embedded therein and having a Shore A hardness offrom about to about 98 on the inner Wall of the socket and adjacent theball.

2. The assembly of claim 1 wherein the coating is on a bearing cup whichforms a Wall of the socket.

3. The assembly of claim 2 wherein the bearing cup is made from sinteredmetal.

4. A ball and socket joint having a socket and a ball positioned in thesocket, a self-adhering coating comprising a substantially non-porouspolyurethane elastomer containing molybdenum disulfide, silicone oil anda hydrocarbon on the inner Wall of the socket and adjacent the ball.

5. IIn a method for making a ball and socket joint, the improvement ofwhich compnises coating at least part of the inner wall of the socketwith a self-adhering coating comprising a substantially non-porouspolyurethane elastomer containing molybdenum disulde, silicone oil and ahydrocarbon.

6. A ball and socket joint having a housing having a socket and ballpositioned in the socket, a thin selfadhering coating comprising asubstantially nonporous polyurethane elastomer having particles ofmolybdenum disulfide embedded therein and having a Shore A'hardness offrom about 80 to about y98 on the inner Wall of the socket and adjacentto the ball.

References Cited in the lile of this patent UNITED STATES PATENTS York,NY.

1. A BALL AND SOCKET JOINT HAVING A HOUSING HAVING A SOCKET AND A BALLPOSITIONED IN THE SOCKET, A THIN SELFADHERING COATING COMPRISING ASUBSTANTIALLY NON-POROUS